JACKSON, Miss. - Retired NFL quarterback Brett Favre pitches his support for Sen. Thad Cochran in a new TV ad paid for by the U.S. Chamber of Commerce.

It's the latest in a string of celebrity endorsements in a hard-fought and often bizarre race in which a tea-party backed candidate, state Sen. Chris McDaniel, is trying to unseat the former Senate Appropriations chairman in a Republican primary runoff next Tuesday.

The U.S. Chamber of Commerce is spending $500,000 for TV ads to support Cochran, including the Favre spot that started airing Thursday.

"I've learned through football that strong leadership can be the difference between winning and losing," scruffy-bearded Favre says in the ad. "And when it comes to our state's future, trust me: Mississippi can win and win big with Thad Cochran as our strong voice in Washington."

Former GOP presidential candidates Sarah Palin, Rick Santorum and Ron Paul have been to Mississippi to campaign for McDaniel, as have the parents from the reality show "19 Kids and Counting," Jim Bob and Michelle Duggar, and their oldest son, Josh Duggar, director of the lobbying arm of the conservative Family Research Council.

Chuck Woolery, who hosted TV game shows such as "Love Connection" and "The Dating Game" and is now a prolific conservative on social media, is scheduled to campaign for McDaniel as part of a Tea Party Express bus tour that starts Friday in McDaniel's home county.

Republican Gov. Phil Bryant and former Sen. Trent Lott have done TV ads for Cochran, and the incumbent's campaign says Sen. John McCain will stump for Cochran on the Gulf Coast on Sunday.

The celebrity endorsements add another twist to a campaign characterized by bizarre happenings that have nothing to do with governing. In mid-May, four McDaniel supporters were arrested and charged in what police describe as a plot to illegally photograph Cochran's wife in the nursing home where she has lived for years with dementia; a photo was briefly posted online in late April in an anti-Cochran video. That case awaits grand jury consideration.

After the June 3 primary, three McDaniel campaign representatives became trapped in a locked county courthouse in the middle of the night, hours after officials had stopped their initial vote count. No criminal charges were filed.

As for Favre, he grew up in the small Mississippi coastal town of Kiln and now lives outside Hattiesburg. In the ad, he says Cochran "always delivers, just like he did during Katrina." It's a reference to billions of federal dollars that Mississippi received after Hurricane Katrina left a wide swath of destruction across the southern half of the state in 2005.

Citizens United Political Victory Fund says it is spending $100,000 to air a pro-McDaniel ad with Santorum speaking directly to the camera about challenges in Washington: "Reckless spending, soaring national debt and repealing Obamacare. But, we can overcome these challenges by sending new conservative leaders to tackle them. Chris McDaniel has the courage to fight for our shared values."

Later Thursday, Santorum campaigned with McDaniel at a barbecue in the Jackson suburb of Madison, telling about 250 people that McDaniel will work to simplify the tax code and end wasteful spending on federal programs that trap Americans in poverty. "He understands how government can be very, very cruel and harmful," Santorum said.

And while Cochran is getting support from McCain now, they haven't always had a smooth relationship. Months before McCain won the 2008 GOP presidential nomination, Cochran, who supported Mitt Romney, told the Boston Globe about the Arizona senator: "The thought of his being president sends a cold chill down my spine. He's erratic. He's hot-headed. He loses his temper, and he worries me."

Asked about that Thursday, Cochran campaign spokesman Jordan Russell told The Associated Press that the working relationship between Cochran and McCain has improved: "I guess they buried the hatchet."